1. Field of the Invention
The present invention relates to an electronic device having a heat dissipation structure for efficiently dissipating heat generated from an electronic part or the like.
2. Description of the Background Art
In order to connect by wire parts composing a large-current circuit to each other, a conductive plate having a large electric power capacity what is called a bus bar is used. For an electronic device including a bus bar electrically connecting large-size electronic parts and a printed circuit board on which semiconductor parts and the like are mounted, heat generated from the electronic parts needs to be efficiently dissipated to the outside of the electronic device in order to suppress the temperature increase of the electronic parts to ensure their stable operation. However, in the electronic device including the bus bar and the printed circuit board, a heat transfer path from an electronic part to a heat dissipation member is local, such as a contact portion of the printed circuit board and the heat dissipation member, with respect to the surface area of the heat dissipation member on the side of the inside of a case of the electronic device, so heat transfer to the whole heat dissipation member is difficult. Thus, conventionally, heat transfer to the outside of the electronic device effectively utilizing the whole surface area of the heat dissipation member has not been achieved.
Furthermore, the heat dissipation structure of conventional electronic devices is such that a heat dissipation area having an increased area is formed at the connection part of GND terminals of electronic parts, such as ICs and semiconductors, on the printed circuit board and a ground line of the board to transfer heat generated from the electronic parts to the heat dissipation area and dissipate heat from the heat dissipation area to the outside. Furthermore, in the conventional electronic devices, in order to enhance heat dissipation capability, the surface area of the heat dissipation area is varied depending on the amount of heat generation, and the heat dissipation area that is a ground line is connected to the heat dissipation member of the electronic device with a heat transfer member, such as a jumper wire or heat conductive harness (for example, see Patent Document 1).    [Patent Document 1] JP-A-2002-111260
However, the heat dissipation structure disclosed in JP-A-2002-111260 has a problem of the increased area of the heat dissipation area causing the board to be large size when the amount of heat generation of the electronic parts is large. Furthermore, in semiconductor devices, such as a power converter mounted on an electric vehicle or HEV, the amount of heat generation from a switching device or the like mounted on the board tends to increase with respect to the conventional electronic devices. Furthermore, as described above, heat is transferred from a large-size and high-heat-generating electronic part, such as a reactor, connected with a bus bar to another electronic part or vice versa through a wiring pattern, so a conventional heat dissipation means alone cannot be expected to sufficiently cool all of the electronic parts.
In other words, the issue is that it is necessary for an electronic device that consumes high amount of power and generates high amount of heat to efficiently cool electronic parts mounted on the board, and furthermore, not limited to the electronic parts, but all of the parts connected by a wiring pattern in order to reliably prevent false operation, distortion, shortened life and noise generation due to the temperature increase of all of the electronic parts.